title: Na3.88Mo15Se19: a novel ternary reduced molybdenum selenide containing Mo6 and Mo9 clusters.
abstract: The structure of tetrasodium penta-deca-molybdenum nona-deca-selenide, Na3.88Mo15Se19, is isotypic with the In3+x Mo15Se19 compounds [Grüttner et al. (1979 ▶). Acta Cryst. B35, 285-292]. It is characterized by two cluster units, Mo6Se (i) 8Se (a) 6 and Mo9Se (i) 11Se (a) 6 (where i represents inner and a apical atoms), that are present in a 1:1 ratio. The cluster units are centered at Wyckoff positions 2b and 2c and have point-group symmetry -3 and -6, respectively. The clusters are inter-connected through additional Mo-Se bonds. In the title compound, the Na(+) cations replace the trivalent as well as the monovalent indium atoms present in In3.9Mo15Se19. One Mo, one Se and one Na atom are situated on mirror planes, and two other Se atoms and one Na atom [occupancy 0.628 (14)] are situated on threefold rotation axes. The crystal studied was twinned by merohedry with refined components of 0.4216 (12) and 0.5784 (12).
authors.affiliation: Faculty of Science III, Lebanese University, PO Box 826, Kobbeh-Tripoli, Lebanon.
authors.forename: Diala
authors.initials: D
authors.lastname: Salloum
authors.forename: Patrick
authors.initials: P
authors.lastname: Gougeon
authors.forename: Philippe
authors.initials: P
authors.lastname: Gall